High intensity sweeteners possess sweetness level many times exceeding that of sucrose. They are essentially non-calorie and used widely in manufacturing of diet and calorie-reduced food. Although natural caloric sweetener such as sucrose, fructose, and glucose provide the most desirable taste to consumers, they are caloric. High intensity sweeteners do not affect the blood glucose level and provide little or no nutritive value.
However, high intensity sweeteners that generally are used as sucrose substitutes possess taste characteristics different than that of sugar, such as sweet taste with different temporal profile, maximal response, flavor profile, mouthfeel, and/or adaptation behavior than that of sugar. For example, the sweet taste of some high-potency sweeteners is slower in onset and longer in duration than that of sugar and thus changes the taste balance of a food composition. Because of these differences, usage of high-potency sweetener in replacing such a bulk sweetener as sugar in a food or beverage causes disbalance in temporal and/or flavor profile. If the taste profile of high-potency sweeteners could be modified to impart desired taste characteristics, it can provide low calorie beverages and food products with taste characteristics more desirable for consumers.
On the other hand, high-potency sweeteners may have some cost and functional advantages compared to sugar. The competition among sugar and non-sugar high-potency sweeteners is tough in soft drinks industry, in countries where their use and production is permitted and also in countries with overvalued sugar prices.
At present high intensity sweeteners are used worldwide. They can be of both synthetic and natural origin.
Non-limiting examples of synthetic sweeteners include sucralose, potassium acesulfame, aspartame, alitame, saccharin, neohesperidin dihydrochalcone synthetic derivatives, cyclamate, neotame, dulcin, suosan, N—[N-[3-(3-hydroxy-4-methoxyphenyl)propyl]-L-α-aspartyl]-L-phenylalanine 1-methyl ester, N—[N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-L-α-aspartyl]-L-phenylalanine 1-methyl ester, N—[N-[3-(3-methoxy-4-hydroxyphenyl)propyl]-L-α-aspartyl]-L-phenylalanine 1-methyl ester, salts thereof, and the like.
Non-limiting examples of natural high intensity sweeteners include Stevioside, Rebaudioside A, Rebaudioside B, Rebaudioside C, Rebaudioside E, Rebaudioside Steviolbioside, Dulcoside A, Rubusoside, mogrosides, brazzein, neohesperidin dihydrochalcone (NHDC), glycyrrhizic acid and its salts, thaumatin, perillartine, pernandulein, niukuroziosides, baiyunoside, phlomisoside-I, dimethyl-hexahydrofluorene-dicarboxylic acid, abrusosides, periandrin, carnosiflosides, cyclocarioside, pterocaryosides, polypodoside A, brazilin, hernandulcin, phillodulcin, glycyphyllin, phlorizin, trilobtain, dihydroflavonol, dihydroquercetin-3-acetate, neoastilibin, trans-cinnamaldehyde, monatin and its salts, selligueain A, hematoxylin, monellin, osladin, pterocaryoside A, pterocaryoside B, mabinlin, pentadin, miraculin, curculin, neoculin, chlorogenic acid, cynarin, siamenoside and others.
At present about eleven high intensity sweeteners are used worldwide. These are acesulfame-K, alitame, aspartame, cyclamate, glycyrrhizin, NHDC, saccharin, Stevioside, sucralose, thaumatin, neotame, and Rebaudioside A.
The standard sweetening power associated with each high intensity sweetener is given in TABLE 1. However, when they are used in blends, the sweetening power can change significantly.
TABLE 1SweetenerSweetness powerSaccharose1Acesulfame-K200Alitame2000Aspartame200Cyclamate30Glycyrrhizin50NHDC1000Saccharine300Stevioside200Rebaudioside A450Thaumatin3000Sucralose600
On the other hand, ‘natural’ and ‘organic’ foods and beverages have become the “hottest area” in the food industry. The combination of consumers' desire, advances in food technology, new studies linking diet to disease and disease prevention has created an unprecedented opportunity to address public health through diet and lifestyle.
A growing number of consumers perceive the ability to control their health by enhancing their current health and/or hedging against future diseases. This creates a demand for food products with enhanced characteristics and associated health benefits, specifically a food and consumer market trend towards “whole health solutions” lifestyle. The term “natural” is highly emotive in the world of sweeteners and has been identified as one of key trust, along with “whole grains”, “heart-healthy” and “low-sodium”. ‘Natural’ term is closely related to ‘healthier’.
In this respect, natural high intensity sweeteners can have better commercial potential.
Stevia rebaudiana Bertoni is a perennial shrub of the Asteraceae (Compositae) family native to certain regions of South America. The leaves of the plant contain from 10 to 20% of diterpene glycosides, which are around 150 to 450 times sweeter than sugar. The leaves have been traditionally used for hundreds of years in Paraguay and Brazil to sweeten local teas and medicines.
At present there are more than 230 Stevia species with significant sweetening properties. The plant has been successfully grown under a wide range of conditions from its native subtropics to the cold northern latitudes.
Steviol glycosides have zero calories and can be used wherever sugar is used. They are ideal for diabetic and low calorie diets. In addition, the sweet steviol glycosides possess functional and sensory properties superior to those of many high potency sweeteners.
The extract of Stevia rebaudiana plant contains a mixture of different sweet diterpene glycosides, which have a single base—steviol and differ by the presence of carbohydrate residues at positions C13 and C19. These glycosides accumulate in Stevia leaves and compose approximately 10%-20% of the total dry weight. Typically, on a dry weight basis, the four major glycosides found in the leaves of Stevia are Dulcoside A (0.3%), Rebaudioside C (0.6-1.0%), Rebaudioside A (3.8%) and Stevioside (9.1%). Other glycosides identified in Stevia extract include Rebaudioside B, D, E, and F, Steviolbioside and Rubusoside. Among steviol glycosides only Stevioside and Rebaudioside A are available in commercial scale.
The physical and sensory properties are well studied only for Stevioside and Rebaudioside A. The sweetness potency of Stevioside is around 210 times higher than sucrose, Rebaudioside A in between 200 and 400 times.
Generally production of extract includes extraction of plant material with water or water-organic solvent mixture, precipitation of high molecular weight substances, deionization, and decolorization, purification on specific macroporous polymeric adsorbents, concentration and drying.
Purification techniques include re-crystallization from various organic solvents as well as chromatographic separation. As a result, besides the highly purified steviol glycosides, substantial amount of by products with 65-75% steviol glycosides content is being generated. The amount of such “non-food grade” materials often exceeds the “main” product 2-3 times and there is a certain economic demand for re-processing of these “by-products”. This possesses big technical challenge as the majority of existing commercial purification processes fail to deliver satisfactory results with initial materials containing as low as 65-75% total steviol glycosides.
On the other hand commercial preparations of steviol glycosides such as Stevia Extract, Rebaudioside A possess certain drawbacks substantially limiting their usage in mainstream products.
One of these disadvantages is “so-called” limited maximal response value. This is the maximal sweetness in sugar equivalents achievable by using a high intensity sweetener regardless how high the concentration of the sweetener is. For steviol glycosides this value is approx. 6-8%. This means when used “as-is” steviol glycosides cannot deliver sweetness feeling which is higher than that of 6-8% sucrose solution. Considering that majority of soft drinks contain 10-13% sucrose the usage of steviol glycosides for full sugar substitution is not possible.
It has to be noted that high intensity sweeteners' taste profile is highly dependant on the concentration and usually the higher the concentration the higher the sensation of undesirable taste components such as bitterness, licorice, lingering aftertaste. This phenomenon limits the usage of steviol glycosides further to 4-5% sucrose equivalents in order to achieve pleasant taste of a food or beverage sweetened with stevia sweeteners.

Rebaudioside C(CAS No: 63550-99-2), also known as Dulcoside B, is the third most abundant sweet glycoside found in Stevia rebaudiana. Nevertheless its isolation and purification are one of the most challenging compared to other glycosides. Few descriptions exist in literature of processes yielding high purity Rebaudioside C.
However recent studies show that highly purified forms of Rebaudioside C possess certain valuable properties. Particularly Rebaudioside C is capable to deliver flavor and sweetness enhancing properties.
These properties multiply the significance of Rebaudioside C and attract great interest for processes of preparation of highly purified forms of Rebaudioside C.
There are few processes described in the prior arts for Rebaudioside C preparation.
U.S. Pat. No. 4,353,889 describes a process of preparation of a substance referred as “Rebaudioside C”. According to the embodiment of the patent, Rebaudioside A is refluxed with strong base in aqueous methanol medium at elevated temperature. Upon completion of the reaction the mixture is cooled and acidified with sulfuric acid to yield the base hydrolysis product called “Rebaudioside C” with 99% purity. It has to be noted that the chemical formula of the compound given in the patent actually corresponds to substance currently known to art as Rebaudioside B (CAS No: 58543-17-2).
Stevia rebaudiana aqueous extract was re-crystallized from methanol-ethanol mixture and Rebaudioside C was recovered from obtained mixture by chromatography on silica gel (Kobayashi et al., 1977). The process employs chromatographic separation which is not suitable for application in commercial scale.
Stevia rebaudiana methanolic extract was re-crystallized from methanol and Rebaudioside C was recovered from obtained mother liquor by chromatography on silica gel (Sakamoto et al., 1977). Using chromatographic separation stage in process makes it difficult to apply in commercial scale.
Most of the existing processes of highly purified Rebaudioside C preparation employ techniques which are only applicable for laboratory or pilot scale production.
However, there is no published data on the commercial isolation and purification of Rebaudioside C.
Hence, there is a need for a simple, efficient, and economical process for production of high purity Rebaudioside C.
Also there's a need for commercial re-processing process for low purity by products obtained after purification of steviol glycosides from raw extract.